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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Bisoxazoline-pincer ligated cobalt-catalyzed hydrogenation of alkenes

The efficient and atom economical hydrogenation of alkenes using a novel bisoxazoline ligated cobalt complex has been developed here. The hydrogenation of a variety of alkenes containing electron neutral and electron-donating groups proceeds in high yield, while electron-withdrawing and sterically hindered groups are not tolerated. Heterocycles and internal alkenes were further hydrogenated in moderate to high yields. While the catalyst is enantiopure, no enantioinduction was observed suggesting that other factors are involved in achieving enantiocontrol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Direct Observation of Elusive (DTBM‐SEGPHOS)CuH Monomer Enables Mechanistic Insights Into Hydrocupration, Aggregation, and Dynamics of Alkene Functionalization Catalysis

The bulky diphosphine DTBM-SEGPHOS is widely employed in CuH-catalyzed transformations as it provides remarkably active catalyst systems. The transient (DTBM-SEGPHOS)CuH monomer (LCuH) is the often-invoked active species. However, its instability has prevented spectroscopic characterization and mechanistic elucidation, hindering mechanistic understanding. We report low-temperature NMR spectroscopic characterization of LCuH, enabling quantitative kinetic analysis of the stoichiometric hydrocupration and catalytic hydroboration of cyclopentene, as well as the structural identification of two CuH clusters. LCuH inserts cyclopentene at −43°C, reaffirming its high reactivity toward olefins. LCuH deactivates to form L 2 Cu 3 H 3 and L 2 Cu 4 H 4 clusters, in which LCuH dimerization initiates aggregation. Kinetic analysis of reactions of unactivated alkenes indicates that competing on-cycle alkene hydrocupration and LCuH dimerization impact performance, as catalyst deactivation and turnover occur on comparable timescales. Structure–activity analysis using atomistic simulations shows that the steric profile of DTBM-SEGPHOS increases the CuH dimerization barrier by ∼7.7 kcal mol−1 compared to that of SEGPHOS, rationalizing the unique ability of DTBM-SEGPHOS to stabilize a reactive monomer for hydrocupration of broader alkene substrates. These findings illustrate the fundamental design principle that steric control of aggregation governs CuH catalyst performance, explaining both the exceptional activity of (DTBM-SEGPHOS)CuH and the limitations imposed by competing deactivation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Two-State Reactivity in Iron-Catalyzed Alkene Isomerization Confers σ-Base Resistance

A low-coordinate, high spin (S = 3/2) organometallic iron(I) complex is a catalyst for the isomerization of alkenes. A combination of experimental and computational mechanistic studies supports a mechanism in which alkene isomerization occurs by the allyl mechanism. Importantly, while substrate binding occurs on the S = 3/2 surface, oxidative addition to an η 1 -allyl intermediate only occurs on the S = 1/2 surface. In conclusion, since this spin state change is only possible when the alkene substrate is bound, the catalyst has high immunity to typical σ-base poisons due to the antibonding interactions of the high spin state.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Fe(porphyrin)-Catalyzed Alkene Epoxidation with NaOCl: A Practical Small- and Large-Scale Alternative to m CPBA

Epoxides are important intermediates in synthetic chemistry. Stoichiometric peroxyacids, such as meta -chloroperoxybenzoic acid ( m CPBA), are widely used to convert alkenes to epoxides but show poor compatibility with aromatic heterocycles and present hazards when scaled. Herein, we report a highly practical alkene epoxidation method that uses the commercially available iron porphyrin, Fe(TPFPP)Cl (TPFPP = tetrakis(pentafluorophenyl)porphyrin), as a catalyst (0.05 mol %) and aqueous NaOCl as the oxidant in acetonitrile as the solvent. No additional ligands or additives are needed, and the reactions proceed under ambient conditions. The method shows a broad scope, affording high yields of epoxides in reactions with terminal and internal aromatic and aliphatic alkenes, heterocycle-containing substrates, glycals, and polyenes. The practicality of the method is demonstrated in the 100 g scale epoxidation of tri- O -acetyl- D -glucal, which proceeds to completion in 15 min at room temperature.

catalysts↗
DOE OSTI2023

Tetrafluorenofulvalene as a sterically frustrated open-shell alkene

Electronic and steric effects are known to greatly influence the structure, characteristics and reactivity of organic compounds. A typical π bond is weakened by oxidation (corresponding to the removal of electrons from bonding orbitals), by reduction (through addition of electrons to antibonding orbitals) and by unpairing of the bonding electrons, such as in the triplet state. Here we describe tetrafluorenofulvalene (TFF), a twisted, open-shell alkene for which these general rules do not hold. Through the synthesis, experimental characterization and computational analysis of its charged species spanning seven redox states, the central alkene bond in TFF is shown to become substantially stronger in the tri- and tetraanion, generated by chemical reduction. Furthermore, although its triplet state contains a weaker alkene bond than the singlet, in the quintet state its bond order increases substantially, yielding a flatter structure. This behaviour originates from the doubly bifurcated topology of the underlying spin system and can be rationalized by the balancing effects of benzenoid aromaticity and spin pairing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Thin-film composite membrane and processes for the separation of alkenes from a gaseous feed mixture

This invention discloses an improved thin-film composite membrane and processes that use the membrane for the separation of gaseous mixtures that include an alkene. The membrane is particularly useful for separation of alkenes from alkanes or the separation of alkenes from other non-hydrocarbon gases. The membrane has a more mechanically durable and defect-free gas-separation layer that is fabricated from an ionomer solution that is substantially free of dissolved ionic species not associated with the ionomer and the mean helium permeability of the thin-film composite membrane is less than two times greater than the intrinsic helium permeability of the gas-separation layer.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Manganese(II) complexes of 1,1'-bis[(pyridin-2-yl)methyl)]-2,2'-bipiperidine (PYBP): Synthesis, structure, catalytic properties in alkene epoxidation with hydrogen peroxide, and related mechanistic studies

In this study, several manganese(II) complexes with the stereoisomers of ligand PYBP (1,1'-bis[(pyridin-2-yl)methyl]-2,2'-bipiperidine) and different anions were prepared and characterized by X-ray diffractometry. Complex [Mn II (rac-PYBP)] 2+ (1) was found to be an efficient catalyst of alkene epoxidation by hydrogen peroxide in the presence of acetic acid in acetonitrile at room temperature. Cyclooctene was converted to its epoxide with up to 91 % yield, 99.6 % selectivity, and the turnover number of 180 within 5 min. Fast epoxidations of cyclohexene, 1-decene, styrene, and cis-stilbene were also achieved. Isomeric complex [Mn II (meso-PYBP)] 2+ (2) was catalytically inactive under the same experimental conditions. Stopped-flow spectrophotometry and freeze-quenched EPR spectra show that complex 2 is not oxidized by H 2 O 2 in the presence of acetic acid (AcOH) but instead undergoes partial ligand protonation and liberation of the Mn 2+ cations due to the relatively poor chelating ability of ligand meso-PYBP. The rac-PYBP isomer acts as a better ligand and retains the coordinated Mn center when complex 1 is treated with the H 2 O 2 /AcOH mixture in acetonitrile solution yielding a mixture of intensely colored intermediates likely involving Mn III , Mn IV , and Mn V complexes. Magnetic susceptibility measurements, UV–vis and EPR spectra suggest that dinuclear complexes [Mn III 2 (μ-O)(μ-OAc)(rac-PYBP) 2 ] 3+ and [Mn III Mn IV (μ-O) 2 (rac-PYBP) 2 ] 3+ gradually accumulate in the reaction mixture as inactivated states of the catalyst. Complex 1 also causes fast decomposition of hydrogen peroxide into O 2 gas and H 2 O, which competes with the epoxidation of alkenes and requires gradual addition of H 2 O 2 for its efficient use. The catalytic activity of complex 1 is strongly influenced by its counterions and decreases in order ClO 4 - ≈ SbF 6 - > NO 3 – > Cl - indicating that labile ligands in the coordination sphere of Mn are required for the activation of H 2 O 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Stereoconvergent Reduction of Activated Alkenes by a Nicotinamide Free Synergistic Photobiocatalytic System

There is a growing interest in developing cooperative chemoenzymatic reactions to harness the reactivity of chemical catalysts and the selectivity of enzymes for the synthesis of nonracemic chiral compounds. However, existing chemoenzymatic systems with more than one chemical reaction and one enzymatic reaction working cooperatively are rare. Moreover, the application of oxidoreductases in cooperative chemoenzymatic reactions is limited by the necessity of using expensive and unstable redox equivalents such as nicotinamide cofactors. Here we report a lightdriven cooperative chemoenzymatic system comprised of a photoinduced electron transfer reaction (PET) and a photosensitized energy transfer reaction (PEnT) with enzymatic reduction in one-pot to synthesize chiral building blocks of bioactive compounds. As a proof of concept, ene-reductase was directly regenerated by PET in the absence of external cofactors. Meanwhile, enzymatic reduction worked cooperatively with photocatalyst-catalyzed energy transfer that continuously replenished the reactive isomer from the less reactive one. The whole system stereoconvergently reduced E/Z mixtures of alkenes to the enantiopure products. Additionally, enantioselective enzymatic reduction worked competitively with photocatalyst-catalyzed racemic background reaction and side reactions to channel the overall electron flow to the single enantiopure product. As a result, such a light-driven cooperative chemoenzymatic system holds great potential for asymmetric synthesis using inexpensive petroleum or biomass derived alkenes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Valorization of waste polyolefins to butene, unsaturated fatty alcohols, and branched alkenes using CO 2 and plasma catalyst

Butene, branched alkenes, and short-chain unsaturated fatty alcohols are among the chemicals that have a wide range of industrial applications in the production of fuels, chemicals, and polymers. In this work, we produced these valuable commodity chemicals from waste plastics using a single-step plasma-catalytic process at atmospheric pressure CO 2 . The study shows that combining non-thermal plasma and zeolite could convert polyolefins at a temperature of 200 °C within 15 minutes, producing liquids rich in C 5 and C 6 branched alkenes and C 6 -C 8 unsaturated fatty alcohols. Additionally, gaseous products include a high yield of butene. Comparative studies indicate that combining CO 2 plasma with zeolite synergistically increases reaction rates and alters product compositions. Product selectivity was strongly dependent on reaction conditions, including plasma power, gas flow rates, reactor temperature, and catalyst loading. Furthermore, this process was applicable to common polyolefins and post-consumer polyethylene, indicating that the plasma catalytic approach has promising potential to valorize waste plastics and greenhouse gas CO 2 into versatile chemicals.

42 ENGINEERING↗
DOE OSTI2022

Catalyst and reactor design considerations for selective production of acids by oxidative cleavage of alkenes and unsaturated fatty acids with H 2 O 2

Oxidative cleavage of alkenes and unsaturated fatty acids with hydrogen peroxide gives an efficient and sustainable process to obtain mono- and di-acids for polymers and lubricants with fewer safety risks and less environmental impact than processes that utilize ozone or other inorganic oxidizers (e.g., permanganate, dichromate, etc.). Guided by insight into the mechanisms for competing reaction pathways (i.e., epoxidation of alkene on W–(η 2 -O 2 ) complexes vs. H 2 O 2 decomposition) and the apparent kinetics derived from kinetic experiments, here, we postulate that W-based heterogeneous catalysts can provide high performance and stable operations at low H 2 O 2 concentrations. Semi-batch reactors with continuous introduction of H 2 O 2 solutions offer the means to maintain low H 2 O 2 concentrations while providing sufficient quantities of H 2 O 2 to satisfy the reaction stoichiometry. We derived simple kinetic model equations for the epoxidation, ring-opening, oxidative cleavage, and oxidation steps and fit theses equations to batch experimental data to obtain kinetic parameters. Furthermore, this kinetic model describes the concentration profiles of reactant, oxidant, and products well as shown by agreement with experimental data. Further predictions of the optimal H 2 O 2 feed rate for semi-batch operation utilized by the proposed rate expressions and the reactor design equations suggest that low H 2 O 2 feed rate increases selectivity towards oxidative cleavage products and selective use of H 2 O 2 for oxidative cleavage pathway. Comparisons of oxidative cleavage of 4-octene in batch and semi-batch reactors show that semibatch reactors with optimized molar feed rates of H 2 O 2 increased oxidative cleavage product selectivities (76% to 99%; with an increase in butyric acid selectivity from 1% to 55%) and H 2 O 2 selectivity (3% to 30%). In addition, semibatch reaction conditions used avoid H 2 O 2 -mediated dissolution of W-atoms from the catalyst. Analysis of these findings suggest that solid oxide catalysts will be effective for continuous oxidative cleavage reactions if deployed within fixed-bed reactors that allow for distributed introduction of reactants and therefore low in situ concentrations of H 2 O 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Data from Stereoconvergent Reduction of Activated Alkenes by a Nicotinamide Free Synergistic Photobiocatalytic System

There is a growing interest in developing cooperative chemoenzymatic reactions to harness the reactivity of chemical catalysts and the selectivity of enzymes for the synthesis of nonracemic chiral compounds. However, existing chemoenzymatic systems with more than one chemical reaction and one enzymatic reaction working cooperatively are rare. Moreover, the application of oxidoreductases in cooperative chemoenzymatic reactions is limited by the necessity of using expensive and unstable redox equivalents such as nicotinamide cofactors. Here, we report a light-driven cooperative chemoenzymatic system comprised of a photoinduced electron transfer reaction (PET) and a photosensitized energy transfer reaction (PEnT) with an enzymatic reduction in one-pot to synthesize chiral building blocks of bioactive compounds. As a proof of concept, ene-reductase was directly regenerated by PET in the absence of external cofactors. Meanwhile, enzymatic reduction worked cooperatively with photocatalyst-catalyzed energy transfer that continuously replenished the reactive isomer from the less reactive one. The whole system stereoconvergently reduced E/Z mixtures of alkenes to the enantiopure products. Additionally, enantioselective enzymatic reduction worked competitively with photocatalyst-catalyzed racemic background reaction and side reactions to channel the overall electron flow to the single enantiopure product. Such a light-driven cooperative chemoenzymatic system holds great potential for asymmetric synthesis using inexpensive petroleum or biomass-derived alkenes.

Catalysis↗
DOE OSTI2022

Data for Catalyst and Reactor Design Considerations for Selective Production of Acids by Oxidative Cleavage of Alkenes with H2O2

Oxidative cleavage of alkenes and unsaturated fatty acids with hydrogen peroxide gives an efficient and sustainable process to obtain mono- and di-acids for polymers and lubricants with fewer safety risks and less environmental impact than processes that utilize ozone or other inorganic oxidizers (e.g., permanganate, dichromate, etc.). Guided by insight into the mechanisms for competing reaction pathways (i.e., epoxidation of alkene on W–(η2-O2) complexes vs. H2O2 decomposition) and the apparent kinetics derived from kinetic experiments, here, we postulate that W-based heterogeneous catalysts can provide high performance and stable operations at low H2O2 concentrations. Semi-batch reactors with continuous introduction of H2O2 solutions offer the means to maintain low H2O2 concentrations while providing sufficient quantities of H2O2 to satisfy the reaction stoichiometry. We derived simple kinetic model equations for the epoxidation, ring-opening, oxidative cleavage, and oxidation steps and fit theses equations to batch experimental data to obtain kinetic parameters. This kinetic model describes the concentration profiles of reactant, oxidant, and products well as shown by agreement with experimental data. Further predictions of the optimal H2O2 feed rate for semi-batch operation utilized by the proposed rate expressions and the reactor design equations suggest that low H2O2 feed rate increases selectivity towards oxidative cleavage products and selective use of H2O2 for oxidative cleavage pathway. Comparisons of oxidative cleavage of 4-octene in batch and semi-batch reactors show that semi-batch reactors with optimized molar feed rates of H2O2 increased oxidative cleavage product selectivities (76% to 99%; with an increase in butyric acid selectivity from 1% to 55%) and H2O2 selectivity (3% to 30%). In addition, semi-batch reaction conditions used avoid H2O2-mediated dissolution of W-atoms from the catalyst. Analysis of these findings suggest that solid oxide catalysts will be effective for continuous oxidative cleavage reactions if deployed within fixed-bed reactors that allow for distributed introduction of reactants and therefore low in situ concentrations of H2O2.

Catalysis↗
NASA NTRS1987

The role of minerals in the thermal alteration of organic matter. IV - Generation of n-alkanes, acyclic isoprenoids, and alkenes in laboratory experiments

The effect of common sedimentary minerals (illite, Na-montmorillonite, or calcite) under different water concentrations on the generation and release of n-alkanes, acyclic isoprenoids, and select alkenes from oil-prone kerogens was investigated. Matrices containing Green River Formation kerogen or Monterey Formation kerogen, alone or in the presence of minerals, were heated at 200 or 300 C for periods of up to 1000 hours, and the pyrolysis products were analyzed. The influence of the first two clay minerals was found to be critically dependent on the water content. Under the dry pyrolysis conditions, both minerals significantly reduced alkene formation; the C12+ n-alkanes and acyclic isoprenoids were mostly destroyed by montmorillonite, but underwent only minor alteration with illite. Under hydrous conditions (mineral/water of 2/1), the effects of both minerals were substantially reduced. Calcite had no significant effect on the thermal evolution of the hydrocarbons.

Huizinga, Bradley J.↗
NASA NTRS1950

Fundamental Flame Velocities of Pure Hydrocarbons I : Alkanes, Alkenes, Alkynes Benzene, and Cyclohexane

The flame velocities of 37 pure hydrocarbons including normal and branched alkanes, alkenes, and alkynes; as well as benzene and cyclohexane, together with the experimental technique employed are presented. The normal alkanes have about the same flame velocity from ethane through heptane with methane being about 16 percent lower. Unsaturation increases the flame velocity in the order of alkanes, alkenes, and alkynes. Branching reduces the flame velocity.

Gerstein, Melvin↗
DOE OSTI2022

Force-Modulated Selectivity of the Rhodium-Catalyzed Hydroformylation of 1-Alkenes

Here we quantify the regio- chemo-, and enantioselectivity of the hydroformylation of 1-alkenes catalyzed by Rh(I) complexes containing chiral macrocyclic biaryl bis(phosphine) ligands as a function of mechanical force applied to the biaryl backbone of these ligands. Extension forces increase the regioselectivity of the hydroformylation of 1-octene from l:b = 1.2 to 1.9 and decrease the chemoselectivity for C 9 aldehyde relative to 2-octene from 96% to 20% across a ~230 pN change in applied force. Extension forces decrease the enantioselectivity of the hydroformylation of styrene from 28% to 18% ee across a similar force range. Variable temperature 1 H and 31 P NMR analysis of five-coordinate rhodium complexes of the form (P–P)Rh(CO) 2 H established structures in which the bisphosphine ligand occupies one equatorial and one apical position in the trigonal bipyramid with rapid interconversion of the equatorial and apical phosphorus atoms ($ΔG^‡_{223 \text{K}}$ = 9.6–9.9 kcal/mol). Neither the isomeric composition nor fluxional behavior of these complexes was detectably perturbed across a ~300 pN change in applied force.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Constraining the Reaction Rate of Criegee Intermediates with Carboxylic Acids during the Multiphase Ozonolysis of Aerosolized Alkenes

Criegee intermediates (CIs) are central to the ozonolysis of unsaturated organic compounds, controlling the formation of small fragmentation reaction products and higher molecular weight oligomeric compounds through competing unimolecular and bimolecular pathways. In particular, the reaction of thermalized CI with carboxylic acids (RCOOH) to produce oligomeric α-acyloxyalkyl hydroperoxides (AAHPs) is of interest to the chemical transformation of organic compounds in the atmosphere. In the gas phase, the CI + RCOOH reaction proceeds at supercollisional rates, consistent with a barrierless reaction mechanism. However, the rate of this reaction in condensed phases remains uncertain. Here, we report the results of aerosol flow tube studies of the ozonolysis of submicron organic aerosol containing mixtures of an internal n-alkene (Z-9-tricosene, tri) and a saturated acid (2-hexyldecanoic acid, HDA). The decay of the reactants and formation of reaction products are monitored using atmospheric pressure chemical ionization mass spectrometry (APCI–MS). A 6-fold decrease in the reactive uptake of ozone is observed with increasing acid concentration, consistent with a previous study using alcohol additives. The decay of HDA with ozone exposure shows that HDA scavenges CIs at rates comparable to competing unimolecular pathways involving CIs. The decay kinetics of HDA are analyzed using a simple kinetic model in order to constrain the ratio of the CI + RCOOH and unimolecular CI rate constants. Empirical fitting to this model, combined with theoretical estimates of the unimolecular loss rate, yields a CI + RCOOH rate constant of 1.85 ± 0.27 × 10 –19 cm 3 molec –1 s –1 , which is six orders of magnitude slower than the expected diffusion limit in a liquid organic matrix. Stochastic kinetic simulations are conducted with different values of the CI + RCOOH rate constant to validate this result and show that the diffusion-limited rate is indeed much too rapid to reproduce the experimental results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Enantioselective Hydrodifluoroalkylation of Alkenes with Conformationally Tuned Peptidyl Hydrogen Atom Transfer Catalysts

Here, we report the enantioselective hydrodifluoroalkylation of alkenes proceeding via an asymmetric hydrogen atom transfer (HAT) event catalyzed by thiol-containing tetrapeptides. Photocatalytic generation of a difluoroacetyl radical followed by carbon–carbon bond formation results in a prochiral carbon-centered radical that engages with the chiral catalyst. A trialkylamine reductant is proposed to turn over the catalyst in this net-reductive transformation. Notably, incorporating an (S)-β-methyl-substituted cysteine as the N-terminal residue improved selectivity relative to that of the native N-terminal cysteine (Cys) residue, and X-ray crystallographic analysis supports the conformational underpinning of this effect. A range of enantioenriched γ-substituted amides were synthesized in up to a 96:4 enantiomeric ratio, demonstrating the broad functional group tolerance of this method. Models accounting for asymmetric induction are proposed with supporting DFT calculations.

08 HYDROGEN↗